RT Journal Article
SR Electronic
T1 Hypocapnia-induced contraction of porcine airway smooth muscle
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP 1046
OP 1052
DO 10.1183/09031936.98.12051046
VO 12
IS 5
A1 KS Lindeman
A1 TL Croxton
A1 B Lande
A1 CA Hirshman
YR 1998
UL http://erj.ersjournals.com/content/12/5/1046.abstract
AB Hypocapnia constricts peripheral airways in vivo. This study investigated the role of airway smooth muscle in this phenomenon and the mechanism of hypocapnia-induced contraction in vitro. Isometric tension, intracellular pH (pHi) and intracellular free calcium concentration ([Ca2+]i) were measured in porcine airway smooth muscles suspended in organ baths in the presence of 5% or 0% CO2. In tracheal strips precontracted with carbachol, hypocapnic challenge (0% CO2) produced increases in tension, pHi, and [Ca2+]i. In bronchial rings or tracheal strips precontracted with carbachol, nifedipine administered between consecutive contractions attenuated responses to hypocapnia (75+/-11% above carbachol-precontracted tension before nifedipine versus 39+/-9% after nifedipine, n=7 bronchial rings, p<0.05). Neither indomethacin (5 microM), nordihydroguaiaretic acid (10 microM) nor phenidone (10 microM) significantly altered responses. These data suggest that enhanced Ca2+ influx through voltage-dependent Ca2+ channels of airway smooth muscle cells is important in airway responses to hypocapnia.